The membrane electrode assembly of a micro fuel cell, which uses high concentration methanol vapor as fuel, encounters numerous challenges. First of all, the high concentration methanol crossover to the cathode results in poisoning the cathode catalyst or resulting in the potential drop. Second, the high concentration methanol feed leads to a lack of key reactant water. Thus the membrane electrode assembly must have water retention. A thinner proton exchange membrane is more favorable for anode water retention and proton conduction. However, the methanol crossover problem becomes even more serious as the thickness of a proton exchange membrane reduces.
To resolve these two critical problems of high concentration methanol crossover and lack of water, the proton exchange membrane must encompass the characteristics of low crossover permeability of methanol and water retention.
The current proton exchange membrane Nafion (a perfluorosulphonic acid resin) forms micro-structures of ion clusters easily. Although these ion clusters are beneficial for proton conduction, but lack of water at high temperature and the problem of methanol crossover are incurred. Hence, Nafion can not be operated under the conditions of high methanol concentration and high-temperature and low humidification. Regarding the perfluorosulphonic acid resin (PFSA) series of proton exchange membrane due to the relationship between humidity, resulting in severe decline of the electrical conductivity, the MEA impedance increased substantially, which led to the MEA performance and durability is poor.